This invention relates to an electric cooker, and more particularly to an electric cooker having a composite heat source composed of an induction heating work coil and an electric heater, and still more particularly to an electric cooker improved in cooling efficiency by improvement of radiation structure.
The typical electric cooker is known as an environment-friendly product that can provide a clean and pleasant cooking environment because of being free from hazardous gas, soot, discharge of carbon monoxide and deficiency of oxygen.
The cooker is also widely used as an energy-efficient product because it takes a short time to reach a maximum thermal power by way of using a new material as heat source, and maintains a constant temperature using a temperature sensor.
An induction heating cooker which is one of the electric cookers is operated in such a manner that a magnetic field is generated by causing high-frequency current to flow through a work coil, and inducing the magnetic field into a cooking vessel, thereby generating eddy current to heat the cooking vessel. Conventionally, this type of induction heating cooker does not generate an air-polluting flame and have a high thermal efficiency, unlike a gas oven stove that heats a cooking vessel by way of oxidizing fuel. Therefore, the demand for this type of induction heating cooker is increasing.
In other words, the induction heating cooker conducts the cooking by using the heat generated by magnetic force applied to the cooking vessel. Therefore, the induction heating cooker is widely accepted as one of the excellent cookers as it generates heat for cooking by using the magnetic field, causing no air pollution and has a high energy usability of 80% or more thermal efficiency.
Meanwhile, the conventional electric cooker includes a cooking plate mounted on an external case, and a heat generating unit as a heat source provided at a bottom surface of the cooking plate. The heat generating unit may be an electric heater, or a typical flat pancake-like radially and spirally wound work coil, or may be a composite heat source using different types of heat sources including the electric heater and the work coil.
In the electric cooker disposed with a composite heat source, an internal temperature of the external case may suddenly increase due to driving heat generated by the electric heater. The rise of internal temperature can affect ambience of the work coil such that there is a need to install heat radiation means for appropriately maintaining the ambient temperature of the work coil having a limit in heat-resistance.
An external case of a typical electric cooker is disposed at an inner space thereof with an inverter (not shown) for driving a heat generating unit, a controller mounted with a driving circuit (not shown) and a cooling unit for cooling the heat generated from the heat generating unit and the controller.
The typical cooling unit of an electric cooker is disposed at one end of the external case thereof with a blowing fan for sucking outside air and blowing the air to the heat generating unit, where the introduced air is horizontally circulated in an inner space of the external case and discharged.
In the ventilation structure of the electric cooker thus explained, the outside air infused by the blowing fan disposed at one end of the external case is horizontally circulated for cooling the heat generating unit and the work coil and sequentially cools the ambient temperature of the work coil and the controller. In other words, the outside air introduced from outside by the blowing fan passes the electric heater to cool the work coil, and again passes the electric heater to cool the controller.
However, there is a disadvantage in the conventional ventilation structure thus explained in that it has a limit of cooling efficiency because the air that has passed the electric heater is used for cooling the work coil and the controller.
There is another disadvantage in that the introduced air is so configured as to horizontally go through a linear passage, making it difficult to effect a uniform cooling operation covering an entire area of the work coil and thereby decreasing the cooling efficiency.
There is still further disadvantage in that a fan of large capacity should be used to enhance the cooling efficiency of an electric cooker having a composite heat source, causing an enlarged size of the cooker and increased manufacturing cost.